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Telnet
_Telnet is an unencrypted, text-based protocol operating over TCP port 23, primarily utilized for remote command-line access to network equipment and servers. Its simplicity allows administrators to manage systems by directly interfacing with their command-line shells; however, due to the lack of security features such as encryption and strong authentication, it has largely been superseded by more secure alternatives._.
Telnet is a legacy protocol standardized by RFC 854, published in 1983, which facilitates bidirectional, interactive, text-based communication between networked devices. It creates a virtual terminal connection that allows a user to execute commands on a remote machine as if they were physically connected via serial console.
Operating primarily over TCP port 23, Telnet establishes a reliable session between a client and a Telnet server, sending plain-text commands and responses encoded in ASCII. It uses a simple byte-stream model with a defined set of command sequences embedded within the data stream, enabling clients and servers to negotiate options like terminal type, echo, and flow control.
Historically, Telnet was extensively employed in managing routers, network switches, UNIX servers, and other infrastructure devices. It remains occasionally used for testing plain-text services, debugging, or legacy maintenance environments, but modern practice strongly discourages its use on untrusted networks due to security concerns.